From d082de574ff13873123c55212ad20cf258ffb283 Mon Sep 17 00:00:00 2001
From: Frank Tang <ftang@chromium.org>
Date: Fri, 15 Sep 2023 16:16:32 -0700
Subject: [PATCH] ICU-22479 Add Fuzzer for DateFormat

---
 icu4c/source/test/fuzzer/Makefile.in          |  2 +-
 .../source/test/fuzzer/date_format_fuzzer.cpp | 52 +++++++++++++++++++
 2 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 icu4c/source/test/fuzzer/date_format_fuzzer.cpp

diff --git a/icu4c/source/test/fuzzer/Makefile.in b/icu4c/source/test/fuzzer/Makefile.in
index da22b464163..9c35674ba75 100644
--- a/icu4c/source/test/fuzzer/Makefile.in
+++ b/icu4c/source/test/fuzzer/Makefile.in
@@ -33,7 +33,7 @@ CPPFLAGS += -I$(srcdir) -I$(top_srcdir)/common -I$(top_srcdir)/i18n -I$(top_srcd
 DEFS += -D'U_TOPSRCDIR="$(top_srcdir)/"' -D'U_TOPBUILDDIR="$(BUILDDIR)"'
 LIBS = $(LIBCTESTFW) $(LIBICUTOOLUTIL) $(LIBICUIO) $(LIBICUI18N) $(LIBICUUC) $(DEFAULT_LIBS) $(LIB_M)
 
-FUZZER_TARGETS = break_iterator_fuzzer calendar_fuzzer collator_compare_fuzzer collator_rulebased_fuzzer converter_fuzzer locale_fuzzer locale_morph_fuzzer number_format_fuzzer ucasemap_fuzzer uloc_canonicalize_fuzzer uloc_for_language_tag_fuzzer uloc_get_name_fuzzer uloc_is_right_to_left_fuzzer uloc_open_keywords_fuzzer unicode_string_codepage_create_fuzzer uregex_open_fuzzer
+FUZZER_TARGETS = break_iterator_fuzzer calendar_fuzzer collator_compare_fuzzer collator_rulebased_fuzzer converter_fuzzer date_format_fuzzer locale_fuzzer locale_morph_fuzzer number_format_fuzzer ucasemap_fuzzer uloc_canonicalize_fuzzer uloc_for_language_tag_fuzzer uloc_get_name_fuzzer uloc_is_right_to_left_fuzzer uloc_open_keywords_fuzzer unicode_string_codepage_create_fuzzer uregex_open_fuzzer
 
 OBJECTS = $(FUZZER_TARGETS:%=%.o)
 OBJECTS += fuzzer_driver.o locale_util.o
diff --git a/icu4c/source/test/fuzzer/date_format_fuzzer.cpp b/icu4c/source/test/fuzzer/date_format_fuzzer.cpp
new file mode 100644
index 00000000000..4578e82f7a3
--- /dev/null
+++ b/icu4c/source/test/fuzzer/date_format_fuzzer.cpp
@@ -0,0 +1,52 @@
+// © 2023 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+
+// Fuzzer for ICU Calendar.
+
+#include <cstring>
+
+#include "fuzzer_utils.h"
+
+#include "unicode/datefmt.h"
+#include "unicode/locid.h"
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+    uint16_t rnd;
+    UDate date;
+    icu::DateFormat::EStyle dateStyle;
+    icu::DateFormat::EStyle timeStyle;
+    if (size < sizeof(rnd) + sizeof(date) + sizeof(dateStyle) + sizeof(timeStyle)) return 0;
+    icu::StringPiece fuzzData(reinterpret_cast<const char *>(data), size);
+
+    std::memcpy(&rnd, fuzzData.data(), sizeof(rnd));
+    fuzzData.remove_prefix(sizeof(rnd));
+    icu::Locale locale = GetRandomLocale(rnd);
+
+    std::memcpy(&dateStyle, fuzzData.data(), sizeof(dateStyle));
+    fuzzData.remove_prefix(sizeof(dateStyle));
+    std::memcpy(&timeStyle, fuzzData.data(), sizeof(timeStyle));
+    fuzzData.remove_prefix(sizeof(timeStyle));
+    std::memcpy(&date, fuzzData.data(), sizeof(date));
+    fuzzData.remove_prefix(sizeof(date));
+
+    std::unique_ptr<icu::DateFormat> df(
+        icu::DateFormat::createDateTimeInstance(dateStyle, timeStyle, locale));
+    icu::UnicodeString appendTo;
+    df->format(date, appendTo);
+    icu::UnicodeString skeleton = icu::UnicodeString::fromUTF8(fuzzData);
+
+    UErrorCode status = U_ZERO_ERROR;
+    appendTo.remove();
+    df.reset(icu::DateFormat::createInstanceForSkeleton(skeleton, status));
+    if (U_SUCCESS(status)) {
+        df->format(date, appendTo);
+    }
+
+    status = U_ZERO_ERROR;
+    appendTo.remove();
+    df.reset(icu::DateFormat::createInstanceForSkeleton(skeleton, locale, status));
+    if (U_SUCCESS(status)) {
+        df->format(date, appendTo);
+    }
+    return EXIT_SUCCESS;
+}